We are requesting funds for the purchase of a state-of-the art fluorescence activated cell sorter (FACS) to support research projects in the newly established Institute of Cancer and Stem Cell Biology and Medicine (ICSCBM) at Stanford University School of Medicine. FACS is the key platform technology for all aspects of this research, including the identification, isolation, and characterization of highly purified subsets of stem and progenitor cells from normal tissues, and cancer stem cells from a wide variety of malignant tissues. The BD Biosciences FACSAria is a benchtop flow cytometer that will be used to carry out the sorting and analysis of these rare cancer and stem cell populations. The acquisition of this instrument is necessary to meet the large and increasing demand for this type of analysis at the ICSCBM. Although there is a shared FACS sorting facility in the Beckman Center, it is highly used and is booked weeks in advance as it services the entire medical school research community. We have established the ICSCBM outside of the medical center at 1050 Arastradero Road, nearby in Palo Alto, and it is important to have an instrument located at this site, both for investigator access and to meet the increasing demand for instrument time. In addition to the studies in mouse models, many of the projects supported by this instrument will rely heavily on human cancer tissues. Many of these samples represent important but rare cancers, and we usually have no more than hours to 1-2 days to prepare for the receipt, preparation and sorting of the live cells. Due to the rarity of the populations sorted in our studies, each sort routinely requires a minimum of two to four hours. These considerations make the orchestration of sorting and/or analysis runs extremely difficult and has considerably retarded the pace of progress. In light of the focus of the ICSCBM and these projects, we feel that there is a pressing need to purchase a readily-available FACS sorter dedicated to these studies. Each of the projects described herein requires multi-parameter sorting capability to fulfill one or more of its aims. Thus, we feel the request for purchase of this essential equipment is well justified. [unreadable] [unreadable]